The present invention relates to a method for determining the driving condition of a vehicle in the event of a failure or absence of a speed sensor, as well as to a device for performing the method.
In the event of a failure or absence of a speed sensor, it would be impossible to distinguish between the moving and stationary condition of a vehicle, which could, for example, detrimentally affect the ability of level and shock-absorber regulators to function.
German Patent Application 19648176 teaches a level-regulating device for regulating the distance between the chassis and the body of an air-cushioned vehicle by controlling the vibration dampers. For such control, an actuating signal is used, which corresponds to a demand for damping the motion of the vehicle body as determined by a known technique.
In order to improve driving safety and comfort, this damping demand is modified by a rough-terrain parameter that describes the road condition. The rough-terrain parameter is computed using the spring-travel acceleration, which is generated by double differentiation of the measured spring travel. The body motions to be damped are defined by determining the rolling angle and rolling frequency, as well as of the pitch angle and the pitch frequency of the vehicle body. This known regulating device is usable to only a limited extent for distinguishing between the moving and stationary condition of a vehicle as well as for determining the frequency of the time variation of the spring travels which may be used for (i) monitoring the plausibility of a driving-speed sensor, and (ii) disabling or enabling any desired functions of an electronically controlled level regulator or an electronic shock-absorber controller or regulator as a function of determined driving condition (stationary or moving) or as a function of determined frequency of the time variation of the spring travels, especially when the spring travels experience a static excursion, as can occur, for example, on uneven terrain or in the case of asymmetric loading, or when the vibrational amplitudes of the spring travels are small, as can occur, for example, during slow driving on smooth roads. Accordingly, it is desired to provide an improved method and apparatus for determining the driving condition of a vehicle in the event of a failure or absence of a speed sensor.
Generally speaking, in accordance with the present invention, an improved method and device is provided for determining the driving condition of a vehicle without using a speed sensor which overcomes disadvantages associated with prior art methods.
To that end, in a vehicle having at least one spring means located between a vehicle body and axle and a travel sensor for sampling spring travels, a method is provided of determining whether the vehicle is moving or stationary including the steps of measuring spring travel values, determining based on the measured spring travel values one of a mean value and a sum value, determining the number of local extrema of the one of a mean value and a sum value within a predefinable observation period, determining the frequency of the local extrema, and comparing the frequency of the local extrema with a predefinable frequency threshold value, such that the vehicle is determined to be moving when the frequency threshold value is exceeded.
Similarly, a device is provided for implementing a method as described. The method and device of the present invention make possible monitoring of the plausibility of driving-speed sensors. Even in the event of a failure or absence of a driving-speed sensor, a distinction between moving and stationary condition can be achieved by the invention. The present invention also makes it possible to determine the vibrational frequency of the spring travel or of the spring travels. As a result, functionalities of level regulators or shock-absorber regulators that must be disabled or enabled during moving or stationary condition or at certain vibrational frequencies of the spring travel or of the spring travels can be disabled or enabled by means of the invention. The inventive method and the inventive device function independently of the static excursion of the spring travel or of the spring travels.
Accordingly, an object of the present invention is to provide a method and a device with which a distinction between moving and stationary conditions of a vehicle can be made, even in the event of the failure or the absence of a driving-speed sensor.
It is a further object of the present invention to provide a method and a device with which a distinction between moving and stationary conditions of a vehicle can be made, even in the event of the failure or the absence of a driving-speed sensor, in order to be able to impose a regulating correction in a level regulator or shock-absorber controller or regulator, for example, and in order to be able to check the plausibility of a driving speed sensor that is present.
Still other objects and advantages of the present invention will in part be obvious and will in part be apparent from the specification.
The present invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and embodies features of construction, combination of elements, and arrangement of parts which are adapted to effect such steps, all as exemplified in the detailed disclosure hereinafter set forth, and the scope of the invention will be indicated in the claims.